The beach at Kalpitiya in Sri Lanka, where there are plans for 10,000 hotel beds. Photograph: Kevin Clogstoun/Getty Images/Lonely Planet Images

British-based travel agencies are among the European holiday firms criticised in a report that alleges tourism development in Sri Lanka is prompting new human rights abuses.

Large-scale tourism developments since the end of thecivil war six years ago have had disastrous effects on local communities, including cases of fishermen losing their access to the sea and allegations of land grabbing by the military, says the report.

Among the travel agencies criticised is Swiss-based Kuoni, which for nearly 50 years has run tours from the UK through 35 branded shops, although it recently unveiled plans to sell its British operation.

The report, Dark Clouds over the Sunshine Paradise, by human rights organisation the Society for Threatened Peoples, urges travel agents to be vigilant about human rights issues.

Sri Lanka is one of the world’s leading holiday destinations – in 2013 it was Lonely Planet’s top pick of countries to visit. More than 1.5 million tourists went there last year, with Britons making up the largest contingent from western Europe, with 144,168 visitors.

The Sri Lankan government has cultivated the image of a country back to normal after a 26-year war that killed an estimated 80,000-100,000 people, with claims that 40,000 Tamil civilians died in the final weeks of the conflict, but the report says the reality is more complicated.

Campaigners examined three new tourist developments – at Kuchchaveli, Passikudah and Kalpitiya, in the north and east of the island, where much of the civil war fighting took place – identifying hotels that they allege undermined the livelihoods of nearby families. They said they had identified 1,200 families that had been adversely affected by the construction of tourist complexes.

The scale of the developments is huge. The project at Kalpitiya aims to establish 10,000 beds in 17 luxury hotels although, the report alleges, “fishermen were denied access to the sea and other lucrative fishing areas” and acres of mangrove were “destroyed where previously women and children had caught prawns and shrimp”.

Researchers also found that land had been taken from locals without prior consultation, with one resident describing how construction work for a luxury hotel began on her land without her being informed.

Despite the claims of human rights infringements, at least 49 German and 21 Swiss travel agencies and a few British subsidiaries offer hotels in the three areas, according to the report.

The Sri Lankan government has considerable ambitions for the tourism trade, drawing up a five-point plan that seeks to attract 2.5 million visitors in 2016, although campaigners say the local population will hardly profit from them.

A Kuoni spokesman said the company was committed to “human rights due diligence” and had conducted impact assessments in a range of destinations. A spokeswoman added: “We welcome the findings from the report and will continue to engage with partners in Sri Lanka to discuss issues and solutions.”

Even though the conflict is over, concerns have been raised over the situation in Sri Lanka, with the then United Nations high commissioner for human rights, Navi Pillay, claiming in August 2013 that the country was displaying “signs of heading in an increasingly authoritarian direction”.

Other sources claim that Tamils detained by Sri Lankan authorities following the end of the conflict suffered sexual and physical abuse, including forced oral sex, anal rape and water torture. The Sri Lankan government revealed recently that it was planning an investigation into accusations of human rights abuses in the late stages of the war.

Mahinda Rajapaksa, who was ousted as president in January, had refused to cooperate with any UN investigation into army atrocities.